Blurry volumetrics in viewport?
Volumetrics is heavily reliant on lighting, so the first thing to do is to place lights accordingly. This is most easily accomplished by using Rendered Preview (shading tab uses Material Preview which uses it's own lighting by default), and to place a light close to your volume.
In addition to lighting, volume &quot;crispness&quot; can be controlled from the Volumetrics section of the Render Properties tab:

Tile size has the largest effect, however it also can also have the largest effect on performance. Increasing the number of samples will increase the detail, and shortening the end value will increase it further (bear in mind - the &quot;end&quot; value is related to your camera distance - too small a value and you won't see the volume except for at very close range.)